BACKGROUND: In patients with dilated cardiomyopathy, the magnitude of cardiac remodeling often correlates with the clinical severity of heart failure. We sought to determine whether measures of left ventricular (LV) dilation and systolic dysfunction in children with dilated cardiomyopathy at the time of listing for cardiac transplantation are associated with survival while waiting for and early after transplant. METHODS AND RESULTS: We analyzed echocardiographic data obtained within 6 months of listing for heart transplant and clinical data from 261 children with dilated cardiomyopathy who were included in both the Pediatric Cardiomyopathy Registry and the Pediatric Heart Transplant Study. Median time to listing after diagnosis was 1.9 months and to transplant after listing was 0.8 months. There were 42 deaths (29 waiting and 13 within 6 months after transplant). We found a significant age-dependent association of LV end-diastolic dimension z score (n=204, 31 deaths) with death controlling for race, transplant status, and medical insurance. The association was strongest for infants younger than 6 months at diagnosis (hazard ratio 1.47, P=0.008) and was not significant in children older than 5 years at diagnosis. A similar interaction was identified between age and LV end-systolic dimension z score (P=0.04). Neither LV function nor mass was associated with death, overall, or in subgroups. CONCLUSIONS: The severity of LV dilation at listing for heart transplant is associated with outcome in infants and young children with dilated cardiomyopathy, whereas the severity of LV systolic dysfunction is not. These findings should be considered in risk stratification of these children at listing.